Various systems have been utilized to provide propulsion for torpedoes. Desirably, such systems should be quiet in operation to prevent or minimize the possibility of premature detection. Further, the system should not be depth sensitive, that is, should be capable of operating in a single, specified fashion whether located just below the surface or substantially below the surface.
Many systems that have been proposed, particularly those utilizing steam turbines, have not met the above criteria. Typically, such systems are open cycle systems where spent or exhaust steam is vented from the torpedo during its operation. Such venting not only increases the noise level of operation, but renders the torpedo sensitive to the depth at which it is running since the back pressure resisting venting will vary proportionately to depth.
To avoid these difficulties, it has been proposed to provide a close cycle steam turbine system particularly suited as the source propulsion for torpedoes. As implied by the term "close cycle", the working fluid, namely water, after it exhausts from the turbine as steam, is condensed and subsequently evaporated to form additional steam for driving the turbine wheel. As a consequence, the working fluid flows throughout a closed path, eliminating any need for venting the same, in turn, eliminating the source of noise associated with venting as well as sensitivity to depth.
At the same time, a closed cycle requires that the turbine exhaust be sealed to a condenser in such a way that the sealed interface will accommodate substantial thermal growth due to the temperture differential between non-operating temperature and operating temperature. To provide such a seal, as well as other necessary components such as engine mounts for the turbine with a minimum number of components, and yet provide a desired degree of reliability in operation, is a considerable task; and the present invention is directed to accomplishing that task.